Office of Compensation Analysis and 

Support 

Technical Information Bulletin

Document Number: OCAS-TIB-014

Effective Date: 12/07/2006

Revision No. 0 

Rocky Flats Internal Dosimetry Coworker Extension Page 1 of 17 

Document Owner: David Allen 

Approval: Signature on File Date: 12/07/2006

 J.W. Neton, Associate Director for Science 

Supersedes: None 

RECORD OF ISSUE/REVISIONS 

ISSUE 

AUTHORIZATION 

DATE 

12/07/2006

EFFECTIVE 

DATE 

12/07/2006 

REV. NO. 

0 

DESCRIPTION 

New document initiated by David Allen to 

extend OTIB-38. 

1.0 INTRODUCTION

Technical Information Bulletins (TIBs) are general working documents that provide 

guidance concerning the preparation of dose reconstructions at particular sites or 

categories of sites. They will be revised if additional relevant information is obtained. 

TIBs may be used to assist the National Institute for Occupational Safety and Health 

(NIOSH) in the completion of individual dose reconstructions. 

In this document the word “facility” is used as a general term for an area, building, or 

group of buildings that served a specific purpose at a site. It does not necessarily 

connote an “atomic weapons employer facility” or a “Department of Energy1

 [DOE] 

facility” as defined in the Energy Employees Occupational Illness Compensation 

Program Act of 2000 [42 U.S.C. § 7384l(5) and (12)]. 

A Technical Information Bulletin (TIB) that analyzes Internal Dosimetry Co-worker data 

at the Rocky Flats Environmental Technology Site (RFETS) was previously completed 

(ORAUT 2006). That document analyzed the data from the beginning of operations at 

the site to 1988. For that effort, data was obtained from the Comprehensive 

Epidemiologic Data Resource (CEDR) repository of data. 

In order to extend the analysis beyond 1988, data was obtained from the Rocky Flats 

site’s HIS-20 database. The purpose of this TIB is to extend the previous TIB (ORAU 

2006) utilizing the same methodology. 

2.0 PURPOSE

Some employees at DOE sites were not monitored for internal ionizing radiation 

exposure or the records of such monitoring are incomplete or unavailable. In such 

 

1

 References to DOE in this document include DOE and its predecessor agencies: the Manhattan Engineer 

District (1942 to 1946), the U.S. Atomic Energy Commission (1947 to 1975), the Energy Research and 

Development Administration (1975 to 1977), and DOE (1977 to the present). 
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Technical Information Bulletin

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Effective Date: 12/07/2006 Revision No. 0 Page 2 of 17 

cases, data from monitored coworkers can be used to estimate an individual’s possible 

exposure. The purpose of this TIB is to provide monitored coworker information for 

calculating and assigning occupational internal doses to employees at RFETS for whom 

no or insufficient bioassay monitoring records exist. 

3.0 DATA OVERVIEW

Urinalysis data for uranium and plutonium from 1989 to 2005 were extracted from the 

Rocky Flats Plant’s HIS-20 database. Both the uranium and plutonium results were 

recorded as dpm/24 hr. Values were recorded as indicated by the analysis, that is, the 

actual results of the analyses were recorded even if it was a negative number. Since 

this analysis assumes the data can be represented by a lognormal distribution, the data 

had to be log transformed. This required the zero and negative results to be treated as 

censored values. 

In vivo 241Am lung data was not addressed in this TIB. The number of samples 

dropped significantly in 1990. 

Bioassay data were analyzed by quarter or year, depending on the amount of data 

available during the periods. A lognormal distribution was assumed. After log 

transforming the data, the 50th and 84th percentiles were determined for each period 

using the method described in ORAUT (2004a). Tables A-1 and A-2 in Attachment A 

show the statistical analysis results for uranium and plutonium respectively. 

4.0 INTAKE MODELING

This section discusses intake modeling assumptions, intake fitting, and the intake 

materials (uranium and plutonium). 

4.1 ASSUMPTIONS 

Each result used in the intake calculations was assumed to be normally distributed. A 

uniform absolute error of 1 was applied to all results, thus assigning the same weight to 

each result. Because of the nature of work at RFETS, it is possible that intakes could 

have been either chronic or acute. However, a series of acute intakes can be 

approximated as a chronic intake. Therefore, intakes were assumed to be chronic and 

were assumed to occur through inhalation, using a default breathing rate of 1.2 m3

/hr 

and a 5-μm activity median aerodynamic diameter particle size distribution. 

4.2 BIOASSAY FITTING 

The IMBA Expert OCAS-Edition computer program was used to fit the bioassay results 

to a series of inhalation intakes. Data from 1989 through 2005 were fit as a series of 

chronic intakes. 

The intake assumptions were based on patterns observed in the bioassay data. Periods 

with constant chronic intake rates were chosen by selecting periods where the bioassay 

results were similar. A new chronic intake period was started if the data indicated a 
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Technical Information Bulletin

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significant sustained change in the bioassay results. By this method, 1989 through 2005 

was divided into multiple chronic intake periods. 

4.3 MATERIAL TYPES 

ORAUT (2004c) discusses Rocky Flats internal dosimetry data for the dose 

reconstructor, including guidance for the appropriate use of that information. Workers at 

Rocky Flats had the potential to receive intakes of plutonium, americium, enriched 

uranium, and depleted uranium. Site-specific internal dosimetry information for other 

radionuclides is rare or not available (ORAU 2004c). 

4.3.1 Uranium

Because the uranium isotopes present at RFETS have very long radiological half-lives, 

and the material is retained in the body for long periods, excretion results are not 

independent. For example, an intake in the 1950s could contribute to urinary excretion 

in the 1980s and later. To avoid potential underestimation of intakes for people who 

worked at RFETS for relatively short periods, each chronic intake was fit independently, 

using only the bioassay results from the single intake period. This method will result in 

an overestimate of intakes for exposures extending through multiple assumed intake 

periods. Only the results within the intake period were selected for use in fitting each 

period. Excluded results are shown in light gray in the figures in Attachment B. 

Uranium urinalysis results were analyzed with IMBA to derive intake rates for 1989 to 

2005. Excretion data are shown in Table A-1. The solid lines in Figures B-1 and B-2 

show the individual fits to the 50th-percentile excretion rates for type F material. Figure 

B-3 is the combined fit for all the intake periods. Figure B-4 shows the overall fit to the 

84th-percentile excretion rates for type F material. The same intake periods were 

applied for both percentiles because the values followed a similar pattern. Similarly, 

Figures B-5 and B-6 show the individual fits to the 50th-percentile excretion rates for 

type M material. Figure B-7 is the combined fit for all the intake periods. Figure B-8 

shows the overall fit to the 84th-percentile excretion rates for type M material. Figures 

B-9 and B-10 show the individual fits to the 50th-percentile excretion rates for type S 

material. Figure B-11 is the combined fit for all the intake periods. Figure B-12 shows 

the overall fit to the 84th-percentile excretion rates for type S material. Table B-1 

tabulates the derived intake rates for Types F, M, and S materials at both the 50th and 

84th percentiles levels along with the associated GSDs. 

4.3.2 Plutonium

Plutonium urinalysis results were analyzed with IMBA using type M and S materials to 

derive intake rates for 1989 to 2005. Figures B-13 and B-14 show the individual fits to 

the 50th-percentile excretion rates for type M material. Figure B-15 is the combined fit 

for all the intake periods. Figure B-16 shows the overall fit to the 84th-percentile 

excretion rates for type M material. The same intake periods were applied for both 

percentiles because the values followed a similar pattern. Table B-2 lists the 50th

percentile and 84th percentile intake rates along with the associated GSD determined 

from plutonium urinalysis for Type M material. 
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Plutonium Type S—Because type S plutonium clears slowly from the lungs, the 

plutonium exposure was fit as a single chronic intake based on the bioassay 

measurements from 1994 through 2005. This period was used because the 

measurements were relatively consistent; in addition, the values are relatively low so the 

intake rate represents a minimum. Figures B-17 and B-18 show the plutonium Type S 

50th- and 84th-percentile excretion rates, respectively. Table B-3 lists the 50th percentile 

and 84th percentile intake rates along with the associated GSD determined from the 

plutonium urinalysis. 

The type S intake rate can only be used as an underestimate. This underestimate 

should be used if the individual was employed after 1988. If the individual’s full 

employment occurred prior to 1989, the underestimated type S intake from ORAUT 2006 

should be used. If an overestimate or best estimate is needed for type S material, an 

individualized fit to the bioassay data for the specific work period of the energy employee 

being evaluated must be performed. Table A-2 provides the bioassay data to be used to 

perform the individualized fit. 

5.0 ASSIGNING INTAKES AND DOSES

This section describes the derived intake rates and provides guidance for assigning 

doses. 

5.1 INTAKE RATE SUMMARY 

Two intake periods were fit to the derived 50th- and 84th-percentile uranium excretion 

data. Table 5-1 summarizes the derived uranium intake rates that produced the fits. 

Two intake periods were fit to the data for type M material and one was fit for type S 

material to the derived 50th- and 84th-percentile plutonium excretion data. Table 5-2 

summarizes the derived plutonium intake rates that produced the fits. Because of the 

interdependence between the bioassay results, it is not possible to fit type S plutonium 

to the data in a manner that would be representative of all individuals for all time 

periods. Therefore, only a minimizing intake has been calculated for type S plutonium. 

Type M plutonium should be applied for all systemic organs. 

For non-systemic (respiratory and GI tracts) organs, the following shall be done: 

1. Run the type M intakes. If this action does not result in a PoC2

 >50%, 

2. Run the minimizing type S intake. The type S intake in this TIB should only be 

used if the individual’s employment includes post 1988 employment. Otherwise, 

the type S intake from ORAUT 2006 should be used. If this action still does not 

yield a PoC >50%, then 

3. Manually fit the coworker bioassay data for the time frame of interest for the 

employee, using the assumption of type S material. 

 

2 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC.
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Standard fitting techniques should be used to fit the plutonium urinalysis data 

from the employee’s work period contained in Table A-2. Acute or chronic 

intakes can be assigned, depending on the patterns in the data. Both the 50thand 84th-percentile data must be fit using the same intake dates or periods; the 

50th-percentile intakes are used to assign the intake and the 84th-percentile is 

used to determine the GSD for each intake. For input into IREP, the dose from 

each intake must be determined separately. 

4. The dose that is more favorable to the claimant from the type M and S fits should 

be assigned. 

Table 5-1. Derived uranium intake rates, 1989 to 2005. 

Type F material Type M material Type S material 

Period 

50th 

percentile 

(dpm/d) 

Geometric 

standard 

deviation 

50th 

percentile

(dpm/d) 

Geometric 

standard 

deviation 

50th 

percentile 

(dpm/d)

Geometric 

standard 

deviation 

1989-1993 0.171 7.98 0.753 7.73 15.11 7.61 

1994-2005 0.038 9.86 0.154 9.93 2.06 10.65 

Table 5-2. Derived plutonium intake rates, 1989 to 2005. 

Type M material 

Period 

50th percentile 

(dpm/d)

Geometric standard 

deviation 

1989-1993 0.780 12.18 

1994-2005 0.053 9.67 

Type S material (underestimate)

Period

50th percentile 

(dpm/d)

Geometric standard 

deviation 

1952-2005 0.245 9.61 

5.2 DOSE ASSIGNMENT 

For most cases, doses to be assigned to individuals are calculated from the 50thpercentile intake rates. Dose reconstructors should select the material type that is the 

most favorable to the claimant. 

The lognormal distribution is selected in the NIOSH Interactive RadioEpidemiological 

Program (IREP), with the calculated dose entered as Parameter 1 and the associated 

GSD as Parameter 2. The GSD is associated with the intake, so it is applied to all 

annual doses determined from the intake period. 
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REFERENCES 

ICRP (International Commission on Radiological Protection), 1995, Dose Coefficients for 

Intakes of Radionuclides by Workers, Publication 68, Pergamon Press, Oxford, 

England. 

ORAUT (Oak Ridge Associated Universities Team), 2004a, Analysis of Coworker 

Bioassay Data for Internal Dose Assignment, ORAUT-OTIB-0019, Rev. 00, Oak 

Ridge, Tennessee. 

ORAUT (Oak Ridge Associated Universities Team), 2004c, Technical Basis Document 

for the Rocky Flats Plant – Occupational Internal Dose, ORAUT-TKBS-0011-5, 

Oak Ridge, Tennessee. 

ORAUT (Oak Ridge Associated Universities Team), 2006, Technical Information Bulletin 

– Internal Dosimetry Coworker Data for Rocky Flats Environmental Technology 

Site, ORAUT-OTIB-0038, Oak Ridge, Tennessee. 
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ATTACHMENT A. COWORKER DATA TABLES 

Table A-1. Summary of uranium urinary excretion rate analyses, 1989 to 2005 

Effective 

sample 

date 

50th 

percentile 

(dpm/24 

hr) 

84th 

percentile 

(dpm/24 hr) 

2/15/1989 0.054 0.726

5/15/1989 0.042 0.337

8/15/1989 0.035 0.258

11/15/1989 0.053 0.290

7/1/1990 0.033 0.212

7/1/1991 0.037 0.187

7/1/1992 0.067 0.678

7/1/1993 0.048 0.278

2/15/1994 0.008 0.071

5/15/1994 0.027 0.182

8/15/1994 0.010 0.100

11/15/1994 0.021 0.126

7/1/1995 0.023 0.124

2/15/1996 0.006 0.075

5/15/1996 0.003 0.047

8/15/1996 0.004 0.042

11/15/1996 0.007 0.047

2/15/1997 0.010 0.067

5/15/1997 0.014 0.076

8/15/1997 0.014 0.060

11/15/1997 0.017 0.060

7/1/1998 0.004 0.024

Effective 

sample 

date 

50th 

percentile 

(dpm/24 

hr) 

84th 

percentile 

(dpm/24 hr) 

7/1/1999 0.008 0.046

2/15/2000 0.007 0.046

5/15/2000 0.004 0.089

8/15/2000 0.004 0.036

11/15/2000 0.005 0.038

2/15/2001 0.010 0.041

5/15/2001 0.011 0.066

8/15/2001 0.007 0.049

11/15/2001 0.006 0.068

2/15/2002 0.009 0.072

5/15/2002 0.016 0.142

8/15/2002 0.012 0.655

11/15/2002 0.009 0.169

2/15/2003 0.006 0.110

5/15/2003 0.012 0.074

8/15/2003 0.003 0.032

11/15/2003 0.014 0.054

2/15/2004 0.018 0.089

5/15/2004 0.015 0.079

8/15/2004 0.008 0.055

11/15/2004 0.007 0.494

7/1/2005 0.012 0.048

All results shown in bold are annual averages rather than quarterly averages
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Table A-2. Summary of plutonium urinary excretion rate analyses, 1989 to 2005 

Effective 

sample 

date 

50th 

percentile 

(dpm/24 hr) 

84th 

percentile 

(dpm/24 hr) 

2/15/1989 0.004 0.035 

5/15/1989 0.011 0.072 

8/15/1989 0.003 0.065 

11/15/1989 0.007 0.085 

2/15/1990 0.002 0.028 

5/15/1990 0.004 0.031 

8/15/1990 0.002 0.031 

11/15/1990 0.004 0.038 

2/15/1991 0.004 0.026 

5/15/1991 0.001 0.063 

8/15/1991 0.008 0.097 

11/15/1991 0.001 0.039 

2/15/1992 0.001 0.019 

5/15/1992 0.003 0.020 

8/15/1992 0.005 0.036 

11/15/1992 0.009 0.107 

7/1/1993 0.004 0.065

2/15/1994 0.000 0.005 

5/15/1994 0.001 0.006 

8/15/1994 0.001 0.007 

11/15/1994 0.001 0.007 

7/1/1995 0.001 0.008

2/15/1996 0.001 0.010 

5/15/1996 0.001 0.007 

8/15/1996 0.000 0.004 

11/15/1996 0.000 0.005 

2/15/1997 0.001 0.007 

Effective 

sample 

date 

50th 

percentile 

(dpm/24 hr) 

84th 

percentile 

(dpm/24 hr) 

5/15/1997 0.001 0.006 

8/15/1997 0.000 0.007 

11/15/1997 0.000 0.001 

7/1/1998 0.000 0.003

7/1/1999 0.000 0.004

2/15/2000 0.000 0.003 

5/15/2000 0.001 0.003 

8/15/2000 0.001 0.003 

11/15/2000 0.000 0.003 

2/15/2001 0.000 0.003 

5/15/2001 0.000 0.004 

8/15/2001 0.000 0.004 

11/15/2001 0.000 0.003 

2/15/2002 0.000 0.004 

5/15/2002 0.000 0.004 

8/15/2002 0.000 0.003 

11/15/2002 0.000 0.003 

2/15/2003 0.000 0.002 

5/15/2003 0.000 0.003 

8/15/2003 0.000 0.003 

11/15/2003 0.000 0.003 

2/15/2004 0.000 0.007 

5/15/2004 0.000 0.003 

8/15/2004 0.000 0.003 

11/15/2004 0.000 0.002 

7/1/2005 0.000 0.003

All results shown in bold are annual averages rather than quarterly averages. 
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ATTACHMENT B. COWORKER DATA FIGURES 

Figure B-1. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/1993, 50thpercentile, Type F. 

Figure B-2. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1994 to 12/31/2005, 50thpercentile, Type F. 
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Figure B-3. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots) from all intakes 1/1/1989 to 

12/31/2005, 50th-percentile, Type F. 

Figure B-4. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/2005, 84thpercentile, Type F. 
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Figure B-5. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/1993, 50thpercentile, Type M. 

Figure B-6. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1994 to 12/31/2005, 50thpercentile, Type M. 
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Figure B-7. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots) from all intakes 1/1/1989 to 

12/31/2005, 50th-percentile, Type M. 

Figure B-8. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/2005, 84thpercentile, Type M. 
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Figure B-9. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/1993, 50thpercentile, Type S. 

Figure B-10. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1994 to 12/31/2005, 50thpercentile, Type S. 
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Figure B-11. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/2005, 50thpercentile, Type S. 

Figure B-12. Predicted uranium bioassay results (line) calculated 

using IMBA-derived U intake rates compared with measured 

uranium-in-urine results (dots), 1/1/1989 to 12/31/2005, 84thpercentile, Type S. 

Table B-1. IMBA-derived uranium intake rates, dpm/day 

Type F Type M Type S 

Years 50% 84% GSD 50% 84% GSD 50% 84% GSD

1989-1993 0.171 1.365 7.98 0.753 5.821 7.73 15.11 115.00 7.61 

1994-2005 0.038 0.370 9.86 0.154 1.531 9.93 2.06 21.95 10.65 
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Figure B-13. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1989 to 12/31/1993, 50th-percentile, 

Type M. 

Figure B-14. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1994 to 12/31/2005, 50th-percentile, 

Type M. 
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Figure B-15. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1989 to 12/31/2005, 50th-percentile, 

Type M. 

Figure B-16. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1989 to 12/31/2005, 84th-percentile, 

Type M. 

Table B-2. IMBA-derived plutonium intake rates, Type M 

Plutonium urinalysisbased results, dpm/day 

Year Pu 50% Pu 84% GSD 

1989-1993 0.780 9.502 12.18

1994-2005 0.053 0.511 9.67
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Figure B-17. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1952 to 12/31/2005, 50-percentile, 

Type S. 

Figure B-18. Predicted plutonium bioassay results (line) calculated 

using IMBA-derived Pu intake rates compared with measured Puin-urine results (dots), 1/1/1952 to 12/31/2005, 84th-percentile, 

Type S. 

Table B-3. IMBA-derived plutonium intake rates, Type S. 

Plutonium urinalysisbased results, dpm/day 

Year Pu 50% Pu 84% GSD 

1952-2005 0.245 2.349 9.61